I would recommend in this case, you measure the OD of the bullets and the ID of the case neck and determine where the problem is.
It isn't that uncommon to find that even jacketed bullets will be a bit smaller than the label says (I would say they could be larger, but I have never seen it).
I have gotten 0.354" 9mm bullets from the "big guys", when the box was clearly labeled 0.355".
Caliper and micrometer will find the cause of many problems.